This procedural macro is intended to parse a rust custom attribute and create user documentation
from it by constructing a DocumentBuilder() automatically. The Documentation can be
retrieved from the documentation() method
declared on AggregateUDF, WindowUDFImpl, ScalarUDFImpl traits.
For doc_section, this macro will try to find corresponding predefined DocSection by label field
Predefined DocSection can be found in datafusion/expr/src/udf.rs
Example: